v2 - Segmentation fault when flushing / indexing a large database

[g1smo]

I got a segfault indexing a large database (92125 songs).

Segfault also happens when restarting the server to flush the oplogs;
Running fpi-server with valgrind -v returns the following:

.......
Applying oplog entry 49475
Applying oplog entry 49476
Reading oplog entries from 49476
No more oplog entries
Index opened
Creating new staging area 3
Persisting operations up to 0 from staging area 2
Searching in staging area 3
Searching in staging area 3
Searching in staging area 2
Searching in staging area 3
Searching in staging area 3
Searching in staging area 2
Searching in main index
==3913184== Thread 12 Thread (pooled):
==3913184== Invalid read of size 8
==3913184==    at 0x4DD9F4C: QMetaObject::invokeMethodImpl(QObject*, QtPrivate::QSlotObjectBase*, Qt::ConnectionType, void*) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==  Address 0x1c9d46b8 is 8 bytes inside a block of size 24 free'd
==3913184==    at 0x48399AB: free (vg_replace_malloc.c:538)
==3913184==    by 0x4E562C1: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E57899: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E567AA: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E56F27: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E56CEC: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E56F27: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E57E4F: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E49830: QJsonDocument::fromJson(QByteArray const&, QJsonParseError*) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x30DE5E: Acoustid::Oplog::read(std::vector<Acoustid::OplogEntry, std::allocator<Acoustid::OplogEntry> >&, int, long) (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x2E4243: Acoustid::Index::open(bool) (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x2E38D9: Acoustid::Index::Index(QSharedPointer<Acoustid::Directory>, bool) (in /opt/acoustid-index-v2/fpi-server)
==3913184==  Block was alloc'd at
==3913184==    at 0x483877F: malloc (vg_replace_malloc.c:307)
==3913184==    by 0x4BFA170: QArrayData::allocate(unsigned long, unsigned long, unsigned long, QFlags<QArrayData::AllocationOption>) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4C4979E: QByteArray::fromRawData(char const*, int) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E56334: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E57899: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E567AA: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E56F27: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E56CEC: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E56F27: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E57E4F: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4E49830: QJsonDocument::fromJson(QByteArray const&, QJsonParseError*) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x30DE5E: Acoustid::Oplog::read(std::vector<Acoustid::OplogEntry, std::allocator<Acoustid::OplogEntry> >&, int, long) (in /opt/acoustid-index-v2/fpi-server)
==3913184==
==3913184== Invalid read of size 8
==3913184==    at 0x4DF9914: QObject::thread() const (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4DD9F50: QMetaObject::invokeMethodImpl(QObject*, QtPrivate::QSlotObjectBase*, Qt::ConnectionType, void*) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x26DE37: _ZN11QMetaObject12invokeMethodIZZZNK8Acoustid6Server10HttpRouter6handleEPN5qhttp6server12QHttpRequestEPNS5_13QHttpResponseEENKUlvE_clEvENKUlvE_clEvEUlvE_EENSt9enable_ifIXaaaantsrN9QtPrivate15FunctionPointerIT_EE25IsPointerToMemberFunctioneqsrSH_13ArgumentCountLin1EntsrSt14is_convertibleISG_PKcE5valueEbE4typeEP7QObjectSG_N2Qt14ConnectionTypeEPDTclfL0p0_EE (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x26DA4C: Acoustid::Server::HttpRouter::handle(qhttp::server::QHttpRequest*, qhttp::server::QHttpResponse*) const::{lambda()#1}::operator()() const::{lambda()#1}::operator()() const (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x26E489: QtConcurrent::StoredFunctorCall0<void, Acoustid::Server::HttpRouter::handle(qhttp::server::QHttpRequest*, qhttp::server::QHttpResponse*) const::{lambda()#1}::operator()() const::{lambda()#1}>::runFunctor() (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x26E843: QtConcurrent::RunFunctionTask<void>::run() (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x4BF1ED1: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4BEEBE0: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x592AEA6: start_thread (pthread_create.c:477)
==3913184==    by 0x585ADEE: clone (clone.S:95)
==3913184==  Address 0x38 is not stack'd, malloc'd or (recently) free'd
==3913184==
==3913184==
==3913184== Process terminating with default action of signal 11 (SIGSEGV)
==3913184==  Access not within mapped region at address 0x38
==3913184==    at 0x4DF9914: QObject::thread() const (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4DD9F50: QMetaObject::invokeMethodImpl(QObject*, QtPrivate::QSlotObjectBase*, Qt::ConnectionType, void*) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x26DE37: _ZN11QMetaObject12invokeMethodIZZZNK8Acoustid6Server10HttpRouter6handleEPN5qhttp6server12QHttpRequestEPNS5_13QHttpResponseEENKUlvE_clEvENKUlvE_clEvEUlvE_EENSt9enable_ifIXaaaantsrN9QtPrivate15FunctionPointerIT_EE25IsPointerToMemberFunctioneqsrSH_13ArgumentCountLin1EntsrSt14is_convertibleISG_PKcE5valueEbE4typeEP7QObjectSG_N2Qt14ConnectionTypeEPDTclfL0p0_EE (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x26DA4C: Acoustid::Server::HttpRouter::handle(qhttp::server::QHttpRequest*, qhttp::server::QHttpResponse*) const::{lambda()#1}::operator()() const::{lambda()#1}::operator()() const (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x26E489: QtConcurrent::StoredFunctorCall0<void, Acoustid::Server::HttpRouter::handle(qhttp::server::QHttpRequest*, qhttp::server::QHttpResponse*) const::{lambda()#1}::operator()() const::{lambda()#1}>::runFunctor() (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x26E843: QtConcurrent::RunFunctionTask<void>::run() (in /opt/acoustid-index-v2/fpi-server)
==3913184==    by 0x4BF1ED1: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x4BEEBE0: ??? (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.15.2)
==3913184==    by 0x592AEA6: start_thread (pthread_create.c:477)
==3913184==    by 0x585ADEE: clone (clone.S:95)
==3913184==  If you believe this happened as a result of a stack
==3913184==  overflow in your program's main thread (unlikely but
==3913184==  possible), you can try to increase the size of the
==3913184==  main thread stack using the --main-stacksize= flag.
==3913184==  The main thread stack size used in this run was 8388608.
==3913184==
==3913184== HEAP SUMMARY:
==3913184==     in use at exit: 3,545,715,273 bytes in 88,572,691 blocks
==3913184==   total heap usage: 364,892,583 allocs, 276,319,892 frees, 20,566,969,158 bytes allocated
==3913184==
Killed